NTRK2 and depressive symptom measurement: Given the importance of prolonged antidepressant and VNS treatments for optimal clinical response in depression, the next experiment examined the effect of longer administration, for 14 days, of VNS, sertraline (7.5 mg/kg/day, i.p) or DMI (10 mg/kg/day, i.p) on the phosphorylation of TrkB.